Impact extrusion is a well-known process, in which a slug of metal (usually aluminum or an aluminum alloy) is placed in a cylindrical die and struck with a punch at high speed and high pressure. The metal of the slug then flows upwardly to form a thin-wall open ended container. Such containers are commonly used in numerous applications, e.g. as beverage containers, aerosol containers, and to hold various other products.
After the container has been formed, the open end is usually formed into a narrowed neck, and a top (e.g. a spray valve) is applied to the container.
Until the present time, the extent to which the neck has been narrowed has been limited, and the narrowed neck of the container has been of relatively short axial dimension. It has not been easily possible to form a long neck of greatly reduced diameter on one piece impact extruded containers, because of the difficulties encountered when forming the material of the neck. Because the material tends to wrinkle and split when being formed, the reject rate has been unacceptably high. Therefore, when containers having elongated narrow necks have been needed, e.g. to contain liquids to be added to automotive fuel or oil, such containers have usually been made from plastic. Plastic containers have the disadvantage that they may be permeable to compounds in the liquids which they are to contain, and they may even be attacked by such liquids.